Most medicaments affecting arterial blood pressure act either via the stimulation of alpha-adrenergic receptors or directly on the visceral muscles of the vascular wall. Adrenomimetics, e.g. adrenaline, noradrenaline, adrianol, phenylephrine (mezaton) ephedrine, ethylephrine, etc., and polypeptides, e.g. glucogon, angiotensin, octapressin, etc. are most often used.
Mezaton is a well known adrenomimetic drug (M. D. Mashkovsky, Medicines, 12-th edd., Moscow., Medicine, 1993, Part I, p. 303), having a pharmaceutical activity related to that of the compounds of the present invention. Mezaton (1-(m-hydroxyphenyl)-2-methylaminoethanol hydrochloride) selectively stimulates .alpha.1-adrenoreceptors, causes arterial constriction and increase in systolic and diastolic pressure (with possible reflectoral bradycardia). Mezaton practically does not have cardiostimulating effect. Unlike adrenaline and noradrenoline, mezaton is not a catecholamine (it contains only one hydroxyl group in aromatic nucleus) and is not influenced by the enzyme--catechole-O-methyltransferase, therefore it is more stable and has a prolonged effect. Mezaton's anti-hypotensive effect usually lasts for approximately 20 minutes after a single intravascular injection.
Adrenomimetics, among them mezaton, have some common shortcomings, as they increase tissue oxygen consumption, cause metabolic acidosis, may cause arrhythmia (especially during general anesthesia), and exert exciting influence on the central nervous system (O. M. Avakyan, Adrenoreceptor function pharmacological regulation, M., Medicine, 1988, p. 8; V. G. Kulinsky, A. N. Kovalevsky, Bulletin of Experimental Biological Medicine, 1984, p. 9). The appearance of secondary hypotension is characteristic of them. Adrenomimetics do not correct arterial hypotension caused by adrenergic blocking agents, and have only a slight anti-hypotensive effect in case of metabolic acidosis (C. Kortanje, V. I. Mathy, R. Charldorp, Haunyn-Gchinedeleg in Arch. Pharmacol., 330:3, 187-192 (1985)).
Medicaments with polypeptide structure have a short adrenomimetic effect. To achieve prolonged effect they are injected in the form of perfusion (I. M. Autkunson, S. I. Dusting, V. I. Rand, Aust. J. Exp. Biol. Med., 50:847-859 (1972)).
In the pathogenesis of oxygen poisoning, the main function belongs to the adrenoreceptors .beta..sub.1 and .beta..sub.2 which affect the metabolism of catecholamines. A known compound used in hyperoxia experiments on animals is etyron (S-ethylisothiouronium bromide). Etyron was described in the literature (E. A. Mukhin et al., Hypertensive medicines 1983, 118-122) as having a protective activity under increased oxygen pressure.
S-Alkylisothiouronium salts with phosphorus containing acids, among them Difetur (S-ethylisothiouronium diethylphosphate) are described in the art as having distinct radioprotective effect and their toxicological characteristics have been studied (P. G. Zherebchenko, Yu. D. Zilber, G. P. Pospekhov, et al., Radiobiologya, 8:582-587 (1968); Zh. A. Goloschapova, T. N. Tuzhilkova, L. I. Mizrakh, Radiobiology, 21:521-525 (1981)).